A prior locking device for stud nuts is available. This is the "Stud Nut Locking Device" described in U.S. Pat. No. 4,862,716 by Jay. S. Derman. This device is intended primarily for locking spare tires and utilizes a rectangular section tube and a locking assembly that is inserted in the tube until it grasps the wheel stud nut. A cylindrical plug lock, when locked in position, prevents the locking assembly from releasing the wheel stud nut and prevents access to it. The device does not cover the nut from view and is not easily adaptable for locking the heads of bolts or nuts such as are used to hold down seats or other equipment. An improvement to the device, to make it more universally adaptable to the needs of bolted down equipment such as automobile seats and office equipment, would make the device more useful in combatting theft.